1. Field of the Invention
This invention relates to cellulose-based, bulky mats and sheets having good decorative and functioning capabilities which can be molded or shaped for use as building materials such as wall and ceiling materials, vehicles, furniture, decorative articles, filter media, absorption media and the like. The invention also relates to embossed mats and sheets of cellulose-based material and to methods for making such mats and sheets as mentioned above.
2. Prior Art
Known bulky mats and sheets mainly composed of pulp include, for example, non-woven fabrics which are obtained by a dry process wherein fibrillated pulp fibers are bonded together by means of a binder, those non-woven fabrics to which long fibers such as rayon are applied onto one or both surfaces thereof, or sheets obtained by mixing thermally fusible fibers or powder with pulp fibers and thermally bonding the fibers together.
These mats or sheets are bulky but since pulp fibers are used as they are, the bulkiness will be lost when they are in contact with water, with the degree of restoration of the bulkiness being small after re-drying of the once water contacted mats or sheets.
Although there is known a sheet for use as a wall paper which is produced by subjecting a vinyl chloride resin compound containing a foaming agent to foaming by heating and embossing, a cellulose-based embossed sheet has never been known. When these vinyl chloride resin-based sheets having no moisture absorption characteristics are used as a building material, they have no function of controlling humidity and are moisture condensing in nature with an attendant problem of safety at the time of firing in that they emit a very great amount of smoke when burnt and generate a large amount of halogen compound gases.
There is known a technique of making bulky pulp fibers by reaction of the fibers with crosslinking agents. However, this technique has no practical utility because if bulky pulp fibers are made in such a way as mentioned above, fibrillation of the crosslinked fibers results in formation of short fibers and the strength is considerably lowered owing to the reduction in number of the hydroxyl groups by consumption during the crosslinking reaction.